What is cheating?

I knew Dark Souls is a time-consuming game but I was curious about the lore and couldn't play online anyway, so I downloaded a cheat table to play it as fast as I could and just finish the game.

I was using 'Dark souls: Prepare To Die Edition [ FairLight ]' cheat table and I just came back to Firelink Shrine after meeting Gwynevere to go to the Catacombs. Some options were activated but none of them did any harm to the game progress. But I activated All no damage and wanted to see if it works by jumping down the hole Kingseeker Frampt was (I didn't know it doesn't do any damage). I watched the short the cut scene and tried to use bonfire to warp back, but the game suddenly ended and credit rolled. I shut it down but now It starts from the beginning, though I have my items and weapons. But all bosses and NPCs are alive.

Any way to restore my last save? Before the credit? I killed anyone I was able to - like the bonfire keeper who couldn't die duo to some reasons, maybe the progress - in the progress so I don't think there's any other savegame file I can use.

Noobzor

No (at least to my knowledge) Dark Souls are one of the games that are using single save file and unless you haven't made back up save before, you can't move backwards. You just went into New Game+ so basically you are at the start of the game, but if you just want to explore end game areas it's very easy and fast to just rush for bosses without having to fight "trash mobs" - that way you can very fast reach the point of the game you already were at.